Power supply for light-based dermatologic treatment device

ABSTRACT

Switching power supplies made in accordance with the disclosed technology drive flash lamps of dermatologic treatment devices to emit a sequence of relatively small light pulses that are aligned with particular locations within the waveform of the AC line source. Such power supplies not only enable sufficient light energy in aggregate to therapeutically heat target chromophores in a skin region without causing undesired damage to surrounding tissue, but also provide the added benefit that the corresponding electrical energy need not be substantially drawn from any charged capacitor. The disclosed power supply further compensates for performance degradation of the flash lamps during their usable life, by modifying its operation based on predetermined values that are indicative of flash lamp aging/efficiency characteristics. The flash lamps and their associated stored values are preferably incorporated into a replaceable cartridge that facilitates user maintenance of the dermatologic treatment device.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/147,590, filed Aug. 2, 2011, which is the National Stage ofInternational Application PCT/US 10/52664, filed Oct. 14, 2010, whichclaims the benefit of U.S. Provisional Application No. 61/252,369, filedon Oct. 16, 2009, the entireties of which applications are incorporatedherein by reference.

TECHNICAL FIELD

The disclosed technology relates generally to power supply designs forlight-based dermatologic treatment devices and more specifically toswitching power supply circuits capable of repeatedly pulsing a flashlamp to emit a desired amount of therapeutic light energy in suchtreatment devices without any substantial electrical energy beingprovided by a charged capacitor.

BACKGROUND

Electromagnetic energy has been used in a wide range of medicalapplications for many years. In the field of dermatology, lasers, flashlamps/intense pulsed light systems (IPL), and other sources ofelectromagnetic radiation, particularly in the optical radiationwavebands, have been used in dermatologic treatment devices topermanently/temporarily remove hair, promote hair regrowth, treatvascular and pigmented lesions, reduce the appearance of wrinkles, treatacne, remove warts, reduce the appearance of scars, tighten skin,resurface skin, reduce cellulite, remove tattoos, and the like.Light-based dermatologic treatment devices applied to such treatmentsare normally designed to emit therapeutic levels of light energy in acontrolled manner such that one or more light pulses applied to a skinregion exhibit predetermined fluence levels, wavelength ranges, pulsedurations, and inter-pulse delays to achieve a desired therapeuticresult. Failure to properly control the parameters of the emitted lightenergy can result in poor efficacy and/or excessive damage totarget/nontarget tissue.

IPL-based dermatologic treatment devices typically employ switchingpower supplies with pulse forming circuits (also referred to herein aspulse-drive circuits). Unfortunately the pulse forming circuitry in theprior art normally relies on one or more large capacitors that, whendischarged into one or more flash lamps, provide the primary electricalenergy to pulse the flash lamps to emit a therapeutically effectiveamount of light energy. The size, weight, and cost of these relativelylarge capacitors result in cumbersome and expensive treatment devices.Accordingly, continuing research and development is necessary to developsmaller, lighter, and cost-effective dermatologic treatment devices,especially in the consumer market where such concerns are particularlyacute.

SUMMARY

Switching power supplies made in accordance with the disclosedtechnology can drive/pulse the flash lamps of IPL-based dermatologictreatment devices at sufficient levels to achieve a desired therapeuticeffect without incurring the size, weight, and cost limitations ofrelatively large capacitive elements. By driving the flash lamps of thedermatologic treatment device to generate a sequence of relatively smalllight pulses (“small” with respect to fluence and/or pulse duration)aligned with particular locations within the waveform of the AC linesource, the improved power supply not only enables sufficient lightenergy in aggregate to therapeutically heat target chromophores (e.g.,melanin) in a skin region without causing undesired damage tosurrounding tissue, but also provides the added benefit that thecorresponding electrical energy need not be substantially drawn from anycharged capacitor. Consequently, the size, weight, and cost ofdermatologic treatment devices incorporating the disclosed technologycan be significantly reduced.

In one illustrative embodiment, at least some aspects of the disclosedtechnology can be embodied within a dermatologic treatment deviceconfigured to facilitate achievement of a desired cosmetic effect in atarget skin region, such as permanent/temporary hair removal, wrinklereduction, acne reduction, wart removal, increased hair growth,reduction in pigmented or vascular lesions, reduction in appearance ofscars, skin tightening, cellulite reduction, and the like. This improveddevice can include one or more pulse-able flash lamps capable ofemitting sufficient light energy to facilitate achievement of thedesired cosmetic effect. The flash lamp(s) is/are preferably pressurizedwith a noble gas exhibiting desired emission spectrum peaks, such as maybe provided by xenon and/or krypton and can be provided at, for example,one-half atmosphere or more, one atmosphere or more, etc. In someembodiments, at least some of the light energy emitted by the flashlamp(s) can be transmitted to the skin region via an opticallytransparent skin contact element exhibiting a skin contact surface of 2square centimeters or greater. The device further includes a switchingpower supply with at least an AC line voltage detector, a pulse-drivecircuit, and a control circuit.

The AC line voltage detector is in electrical communication with an ACline source and dynamically generates a signal whose duty cycle isindicative of when the voltage of the line source meets or exceeds aminimum operating voltage threshold. This duty cycle is useful inascertaining whether the AC line source is providing high-line orlow-line AC voltage. The signal generated by the AC line voltagedetector can also be indicative of the frequency of the AC line source.

The pulse-drive circuit is in electrical communication with the flashlamp(s) and the AC line source and provides sufficient electrical energyto pulse the flash lamp(s) during its/their simmer state without drawinga substantial amount of electrical energy from a charged capacitor. Oneor more characteristics of the electrical energy (e.g., current level,current pulse duration, and/or inter-pulse delay interval) provided bythe pulse-drive circuit to the flash lamp(s) are based at least partlyon the duty cycle of the signal generated by the AC line voltagedetector. Consequently, the duty cycle or inverse of the duty cycle cansubstantially correspond to a pulse width of the emitted light energy.For example, the duty cycle of the AC line voltage exceeding the minimumoperating voltage threshold can be substantially the same as or greaterthan a pulse width of the emitted light energy. Further, the pulse-drivecircuit may include filter circuitry that mitigates the effect ofelectromagnetic emissions generated by the device on the AC line source,rectifier circuitry that rectifies the electrical energy provided by theAC line source, a current sensor that provides an indication of theelectric current in the flash lamp(s), buck regulator circuitry thatreceives the rectified energy and provides corresponding regulatedelectric current to the flash lamp(s) under the control of the controlcircuit, and a switch in electrical communication with the rectifier andbuck regulator that selectively enables transmission of the rectifiedelectrical energy to the buck regulator.

The control circuit is in electrical communication with the pulse-drivecircuit and AC line voltage detector and selectively enablestransmission of sufficient electrical energy from the pulse-drivecircuit to pulse the flash lamp(s) to emit a therapeutically-sufficientamount of light energy to facilitate achievement of the desired cosmeticeffect. These selective transmissions are based at least partly on thesignal generated by the voltage detector. Further, the control circuitmay include a comparator in electrical communication with the switch andcurrent sensor that generates a signal to control the switch based on acomparison between the indication from the current sensor and areference voltage, and a microprocessor in electrical communication withthe AC line voltage detector and comparator that determines the level ofthe reference voltage based at least partly on the duty cycle of thesignal generated by the voltage detector. The microprocessor modifiesthe reference voltage to ensure that the flash lamp(s) emits/emit lightenergy within a desired fluence range. The microprocessor can furtherdisable the pulse-drive circuit in response to a cooling system failurein the device, a high temperature condition, a user input, a failure tomaintain the device in physical contact with at least one surface of theskin region, an improper configuration condition, and/or a maintenancecondition.

The dermatologic treatment device may also include a simmer circuit thatprovides a low current density to the flash lamp(s) sufficient to enablethe flash lamp(s) to maintain its/their simmer state. A diode in thepulse-drive circuit can be used to prevent any unwanted electricalenergy provided during the simmer state from entering and undesirablyaffecting other elements of the pulse-drive circuit. The device furtherincludes a trigger circuit that provides sufficient electrical energy tothe flash lamp(s) to initiate ionization in the flash lamp(s) at thebeginning of the simmer state.

The dermatologic treatment device is preferably configured such that itscontrol circuit enables the pulse-drive circuit to pulse the flashlamp(s) in a predetermined sequence of light pulses. The sequence oflight pulses can include two or more light pulses (preferably at least 3light pulses) with individual pulse durations between about 1microsecond and 17 milliseconds (preferably between about 4 and 6milliseconds for systems coupled to 60 Hertz AC line sources and betweenabout 4 and 8 milliseconds for systems coupled to 50 Hertz AC linesources) separated by, for example, an inter-pulse delay interval thatis less than the thermal relaxation time of a target within the skinregion, an inter-pulse delay interval that is at least as great as thethermal relaxation time of nontarget tissue (e.g., epidermis), and/orthat is based at least partly on a skin type associated with the skinregion. In some embodiments, the sequence of light pulses is repeatedonce or more times per second (preferably repeated every 0.5 to 0.75seconds). In other embodiments, the sequence of light pulses repeats atintervals greater than one second (e.g., intervals greater than or equalto 2 seconds). In some embodiments, the sequence of light pulses isrepeated at variable intervals based on, for example, one or moretemperature measurements within a handheld housing that contains theflash lamp(s).

Further, the sequence of light pulses is preferably tuned for a desiredcosmetic effect in a skin region. In an illustrative operation in whichtemporary hair removal is desired, the device can be configured suchthat a sequence of light pulses provides an aggregate fluence of thesequence of between about 5-10 J/cm2 (preferably between about 6-8.5J/cm2) to a target skin region with individual pulse widths betweenabout 3-8 ms and inter-pulse delay intervals between about 3-15 ms andincluding wavelengths at least in the range of about 850-1000 nm.

In another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes one or more pulse-able flash lamps, an AC linevoltage detector, and a control circuit. The flash lamp(s) is selectedsuch that it is capable of emitting sufficient light energy tofacilitate achievement of a desired cosmetic effect in a skin region.The AC line voltage detector dynamically generates a signal whose dutycycle is indicative of when an AC line voltage exceeds a minimumoperating voltage threshold. This minimum operating voltage thresholdcorresponds to an electrical energy level sufficient to pulse the flashlamp(s) (while it is in a simmer state) to emit a therapeuticallyeffective amount of light energy to the skin region. The control circuitis in electrical communication with the AC line voltage detector andselectively enables transmission of a desired current through the flashlamp(s) based at least in part on the signal generated by the AC linevoltage detector.

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes one or more pulse-able flash lamps, a memory, and apulse-drive circuit. The flash lamp(s) is selected such that it iscapable of emitting sufficient light energy to facilitate achievement ofa desired cosmetic effect in a skin region. The memory stores one ormore predetermined values that are indicative of one or morecharacteristics of the flash lamp(s). The pulse-drive circuit is inelectrical communication with the flash lamp(s) and repeatedly pulsesthe flash lamp(s) (while it is in a simmer state) to emit atherapeutically effective amount of light energy to the skin region. Theelectrical energy provided by the pulse-drive circuit to the flashlamp(s) does not include any substantial electrical energy from acharged capacitor and is based at least partly on the predeterminedvalue(s) stored in the memory.

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes one or more flash lamps, a memory, and a switchingpower supply. The memory stores one or more predetermined values thatare indicative of one or more characteristics of the flash lamp(s). Theswitching power supply is capable of repeatedly pulsing the flashlamp(s), unrestricted by any capacitor recharge duration and withoutrelying on any substantial energy from a charged capacitor, withsufficient electrical energy to drive the flash lamp(s) to emit asequence of light pulses sufficient to facilitate achievement of adesired cosmetic effect in a skin region. Further, the amount ofelectrical energy provided by the switching power supply is based atleast partly on the predetermined value(s) stored in the memory.

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes one or more pulse-able flash lamps, an AC linevoltage detector, and a pulse-drive circuit. The AC line voltagedetector is in electrical communication with an AC line source anddynamically generates an indication of when the AC line voltage meets,exceeds or is below a minimum operating voltage threshold. Thepulse-drive circuit provides pulsed electrical energy to the flash lamp,which drives the lamp to emit sufficient pulsed light energy tofacilitate achievement of a desired cosmetic effect in a skin region.The pulse width of the pulsed light energy can be made variable based onthe indication generated by the AC line voltage detector.

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes a source of optical radiation (e.g., one or morelasers, light emitting diodes, flash lamps and/or other types of lampsor light emitting elements), a handheld housing containing the opticalradiation source, a temperature sensor that senses one or moretemperatures within the housing (where such temperatures aresubstantially affected by operation of the optical radiation source), apower supply circuit that drives the optical radiation source, and acontrol circuit that controls the power supply based, at least partly,on the sensed temperature. More particularly, the power supply circuitis capable of repeatedly pulsing the optical radiation source such thatthe optical radiation source emits a first sequence of light pulses thatare sufficient to facilitate achievement of a desired cosmetic effect ina skin region. Further, the control circuit can selectively enable thepower supply circuit to pulse the optical radiation source to emit asecond sequence of light pulses, where the time interval between thefirst and second sequences of light pulses is variable based on one ormore temperatures sensed within the handheld housing by the temperaturesensor.

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes one or more flash lamps, a memory (e.g., EEPROM)storing one or more predetermined values indicative of one or morecharacteristics of the flash lamp(s), a replaceable cartridge thatcontains the flash lamp(s) and memory and facilitates periodicreplacement of the flash lamp(s), a power supply capable of energizingthe flash lamp to emit optical radiation sufficient to facilitateachievement of a desired cosmetic effect in a skin region, and a controlcircuit in communication with the power supply and memory thatperiodically causes the power supply to increase the electric currentprovided to the flash lamp(s) based at least partly on the predeterminedvalue stored in the memory. One or more predetermined values stored inthe memory can be indicative of an aging characteristic (e.g., gradualreduction in light output) of the flash lamp(s) and/or of an efficiencyof the flash lamp(s).

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a replaceable cartridge fora light-based dermatologic treatment device, where such replaceablecartridge includes one or more flash lamps and a memory mechanicallycoupled to the flash lamp(s) (mechanical coupling can be achieved, forexample, using a housing of the cartridge that maintains a relativeposition between the flash lamp(s) and memory). The memory stores one ormore predetermined and/or dynamically-generated values that areindicative of one or more characteristics of the flash lamp(s), such asan aging characteristic, an efficiency, a range of filtered wavelengthsemitted by the flash lamp(s) (in which case it is preferable that thereplaceable cartridge is designed for a particular range of skin colorsor skin types), a maximum flash count of the flash lamp(s), and/or aninitial amount of electric current necessary to drive the flash lamp(s)to emit optical radiation sufficient to facilitate achievement of adesired cosmetic effect in a skin region. A predetermined value storedin memory can also be indicative that the flash lamp(s) contained in thereplaceable cartridge is/are authorized for use in such replaceablecartridge. The housing of the replaceable cartridge contains the flashlamp and memory and further includes a vent portion exhibiting alouvered or herringbone cross section, which facilitates cooling of theflash lamp while concurrently blocking at least some light emissionsleaking out of the electrode ends of the flash lamp.

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes one or more pulse-able flash lamps that are capableof emitting sufficient light energy to facilitate achievement of adesired cosmetic effect in a skin region, along with a window adapted toinsulate a skin surface in the skin region from at least some of theunwanted heat generated during operation of the device. The windowpreferably includes a first pane and a second pane of opticallytransparent material with a sealed space defined therebetween. Thesecond pane may include reflective coatings that reflect at least someof the light emissions with wavelengths less than about 600 nanometersback to the flash lamp and is preferably comprised of an opticallytransparent material that absorbs at least some of the flash lamp'sinfrared emissions (e.g. above about 2000 nanometers). The first pane ispreferably comprised of optically transparent material with a hydroxylcomponent of less than or equal to about 5 parts per million and isadapted for placement against a skin surface in the skin region to betreated by the device. The sealed space between the two panes canenclose a vacuum or a quantity of air or other gas.

In yet another illustrative embodiment, at least some aspects of thedisclosed technology can be embodied within a dermatologic treatmentdevice that includes one or more pulse-able flash lamps that are capableof emitting sufficient light energy during a pulse state to facilitateachievement of a desired cosmetic effect in a skin region, along with areflector, optical waveguide, and optically transparent window. Thereflector is optically coupled to the flash lamp(s) and is adapted toreflect at least some of the light energy emitted by the flash lamp(s).The optical waveguide is optically coupled to the reflector and isadapted to convey at least some of the light energy reflected by thereflector. The optically transparent window is optically coupled to theoptical waveguide and is adapted to receive at least some of the lightenergy conveyed by the waveguide. The optical waveguide is normallyspaced apart from the reflector and/or window by a predetermineddistance when the flash lamp is not in its pulse state, but thatdistance is substantially reduced, and in some embodiments substantiallyeliminated, when the flash lamp is in its pulse state (e.g., whenemitting one or more sequences of intense pulsed light). Maintaining thedistance at a predetermined value when the flash lamp(s) is not emittinga light pulse sequence facilitates cooling of the device, whereas asubstantial reduction in the distance during emission of the light pulsesequence improves optical efficiency of the device at the expense oftemporarily decreasing cooling of at least part of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing discussion will be understood more readily from thefollowing detailed description of the disclosed technology, when takenin conjunction with the accompanying drawings, the same or relatedreference numerals being used for like elements in the various drawings,in which:

FIG. 1 provides a three dimensional perspective of an illustrativedermatologic treatment device made and operated in accordance with atleast some aspects of the disclosed technology;

FIGS. 2A-2G provide various perspective views of an illustrativereplaceable light cartridge with dual flash lamps that can be used inthe dermatologic treatment device of FIG. 1, where FIGS. 2A and 2Bdepict the front of the cartridge, FIGS. 2C-2E depict the back of thecartridge along with illustrative pin out configurations, and FIGS.2F-2G depict cross sectional views of the cartridge with illustrativelouvered or herringbone-shaped vent schemes;

FIGS. 3A-3E are substantially identical to FIGS. 2A-2E except that theyillustrate an exemplary embodiment in which the replaceable lightcartridge contains a single flash lamp;

FIG. 4 provides a high level system diagram of a dermatologic treatmentdevice incorporating an illustrative switching power supply operating inaccordance with an embodiment of the disclosed technology;

FIG. 5 provides a flow chart of an illustrative methodology foroperating the dermatologic treatment device of FIG. 4 in accordance withan embodiment of the disclosed technology;

FIG. 6 is a signal diagram illustrating high-line and low-line ACvoltage conditions that may appear on a rectified AC line sourcerelative to a minimum operating voltage threshold sufficient to operatethe dermatologic treatment device of FIG. 4;

FIG. 7 is a signal diagram of an illustrative signal generated by an ACline voltage detector, which is indicative of the frequency andhigh/low-line AC voltage conditions of the rectified AC line sourceshown in FIG. 6;

FIG. 8 is a signal diagram representing an illustrative voltage waveformapplied across one or more flash lamps in a light-based dermatologictreatment device in response to operating the simmer, trigger, andpulse-drive circuits of FIGS. 13-15 under the control of the controlcircuit of FIG. 16 and pursuant to the methodology depicted in FIG. 5;

FIG. 9 is a signal diagram representing an illustrative current waveformpassing through one or more flash lamps and corresponding to the voltagewaveform shown in FIG. 8;

FIG. 10 is a signal diagram representing the light emitted by one ormore flash lamps when such flash lamps are subjected to the voltage andcurrent waveforms of FIGS. 8 and 9;

FIG. 11 provides an illustrative thermal profile of target tissuelocated in a skin region below the epidermis when subjected to the lightemissions depicted in FIG. 10;

FIG. 12 provides an illustrative thermal profile of non-target,epidermal tissue when subjected to the light emissions depicted in FIG.10;

FIG. 13 provides a schematic of an illustrative simmer circuit of apower supply designed for operating a light-based dermatologic treatmentdevice in accordance with an embodiment of the disclosed technology;

FIG. 14 provides a schematic of an illustrative trigger circuit of apower supply designed for operating a light-based dermatologic treatmentdevice in accordance with an embodiment of the disclosed technology;

FIG. 15 provides a schematic of an illustrative pulse-drive circuit of apower supply designed for operating a light-based dermatologic treatmentdevice in accordance with an embodiment of the disclosed technology; and

FIG. 16 provides a schematic of an illustrative control circuit of apower supply designed for operating a light-based dermatologic treatmentdevice in accordance with an embodiment of the disclosed technology.

DETAILED DESCRIPTION

Unless otherwise specified, the illustrated embodiments can beunderstood as providing exemplary features of varying detail of certainembodiments, and therefore, unless otherwise specified, features,components, modules, elements, circuits, and/or aspects of theillustrations can be otherwise combined, interconnected, sequenced,separated, interchanged, positioned, and/or rearranged withoutmaterially departing from the disclosed systems or methods.Additionally, elements illustrated in the drawings are providedprimarily to facilitate understanding of the disclosed technology andare not necessarily drawn to scale.

For the purposes of this disclosure, the term “circuit” refers to aninterconnection of electrical (analog or digital), electronic, optical,acoustic, mechanical, magnetic, electromechanical, electro-optical,optoelectronic, photonic, electromagnetic, and/or electro-acousticelements or the like arranged in substantially any suitable manner orcombination to perform one or more desired functions. Those skilled inthe art will recognize that the functionality described for a particularcircuit can be incorporated into one or more other circuits, thatparticular elements in a circuit can be shared with different circuits,and/or that the circuits themselves can be otherwise combined,interconnected, separated, and/or organized without adversely affectingthe operation of the disclosed technology and thus are intended merelyfor illustrative purposes.

Except as explicitly stated to the contrary, the term, “substantially”can be broadly construed to indicate a precise relationship, condition,arrangement, orientation, and/or other characteristic, as well as,deviations thereof as understood by one of ordinary skill in the art, tothe extent that such deviations do not materially affect the disclosedmethods and systems.

Further, the terms “light” and “optical radiation” are usedinterchangeably and references to “wavelengths” pertain to opticalradiation exhibiting wavelengths of the type described in that context.The terms “device” and “system” are also used interchangeably, as arethe terms “circuit” and “supply.”

Light-based dermatologic treatment devices typically rely on thespectral emissions of one or more lasers, flash lamps, and/or LEDs toprovide sufficient optical radiation to thermally treat a desiredepidermal or dermal condition. Flash lamps, in particular, provide aflexible and cost effective means for generating intense pulsed lightexhibiting a range of desired wavelengths that can be tuned (byfiltration and/or wavelength conversion) to facilitate a desiredcosmetic or non-cosmetic effect in a target skin region.

Flash lamps are gas discharge devices having an optically transparentenvelope (made of, for example, fused quartz/silica, borosilicate, orthe like) that is sealed on each end to an electrode assembly and filledwith a noble gas (e.g., xenon, krypton, etc.) to a desired pressure(e.g., one-half atmosphere, one atmosphere, etc). Prior to emittingoptical radiation, the impedance of the flash lamp is initiallyrelatively high due to the resistivity of the unionized noble gasbetween the cathode and anode. In order to emit optical radiation, thegas in the flash lamp must be ionized, which will also result in adrastically reduced impedance.

Such ionization can be instantiated by applying a high voltage triggerpulse (e.g., 6-10 kilovolts for 200 nanoseconds to 1 millisecond) to theelectrode assembly of the flash lamp using an external, seriesinjection, or pseudo-series injection triggering scheme, as is known tothose skilled in the art. Once the gas is ionized, it emits opticalradiation across a broad spectrum of wavelengths. The amount of opticalradiation emitted is dependent, at least in part, on the degree ofionization of the gas, which is affected by the electrical currentdensity supplied between the electrodes following the trigger pulse.Higher current densities result in intense light emissions (referred toherein as the “pulse state” of the flash lamp), while lower currentdensities cause the ionized gas to appear as a thin streamer of lightbetween the electrodes of the flash lamp (referred to herein as the“simmer state” of the flash lamp). The lifetime of the flash lampdecreases as the duration and peak of electrical energy provided duringthe pulse state increases, with the flash lamp eventually failing via acatastrophic explosion, fracturing of its optically transparentenvelope, or by a gradual reduction in emitted light. When a sequence ofintense light pulses is desired, the flash lamp is preferably operatedin a simmer state, or at a relatively low-intensity level in a pulsestate, during the inter-pulse period so as to reduce the thermal andmechanical shock to the flash lamp, thereby extending its usable life.

Designers of flash lamp based dermatologic treatment devices expendsignificant effort in developing power supplies capable of driving flashlamps to emit optical radiation exhibiting a desired pulse profile whileconcurrently maintaining reliable power supply performance,commercially-reasonable life expectancy of the flash lamps, and a lowdevice/power supply cost. These competing interests are difficult toreconcile and have driven prior art device manufacturers to useexpensive, capacitor-based power supplies that store large amounts ofelectrical energy that drive the flash lamps under microprocessorcontrol—thereby heavily favoring generation of a desired light pulseprofile over device/power supply cost. It is important to note thatprior art devices have traditionally been operated in a clinicalsetting, where cost is an important, but secondary, factor. In contrast,the commercial success of devices targeted at the consumer market isdependent upon achieving adequate treatment efficacy at a much lowercost.

The inventors recognize that there are several light pulse sequencesavailable for any particular dermatologic treatment and that judiciousselection amongst these sequences (and careful timing when instantiatingsuch light pulse sequences relative to the input AC waveform) can bemade, such that the electrical energy provided by a power supply todrive the flash lamp(s) during its pulse state can be drawnsubstantially directly from the AC line and without any substantialelectrical energy being provided from charged capacitors (e.g., lessthan about 10% of the required electrical energy being provided bycapacitors with the remainder being drawn from the AC line), therebyresulting in a low cost and effective dermatologic treatment device thatis commercially viable for the consumer market. For example, thedisclosed technology can be incorporated within an illustrativelight-based, dermatologic treatment device targeted at temporary hairremoval where the AC line source provides 120 volts at 60 Hz (each halfcycle being 8.3 milliseconds in duration) in which case the device canbe configured to emit a light pulse sequence having a plurality ofpulses (e.g., 4 pulses) providing an aggregate fluence on a skintreatment surface of between about 6-8.5 Joules per square centimeterwith each pulse exhibiting a pulse width of up to about 5.8 milliseconds(corresponding to that portion of the 8.3 millisecond AC half cycleabove an illustrative minimum operating voltage threshold) andinter-pulse delay of about 2.5 milliseconds (corresponding to thatportion of the AC half cycle dropping below the minimum operatingvoltage threshold after the peak of the cycle together with the portionof the next AC half cycle that rises up to the minimum operating voltagethreshold). The selection of this illustrative light pulse sequenceenables the bulk of the electrical energy supplied to the flash lampduring its pulse state to be drawn substantially directly from a fullwave, rectified AC line source during a period in which the voltage ofthe AC line is greater than or equal to about 107 volts (correspondingto an illustrative minimum operating voltage threshold). Similarly, anillustrative light pulse sequence (comprising, for example, 3 pulses) inwhich each pulse has a duration of up to about 7 milliseconds with aninter-pulse delay of about 3 milliseconds is suitable in situationswhere the AC line source provides 240 volts at 50 Hz (each half cyclebeing 10 milliseconds in duration).

Further, the disclosed technology can be configured to provide a fixedpulse width for each of the individual pulses in the light pulsesequence and/or a fixed aggregate pulse width for the light pulsesequence itself to ensure repeatability of tightly-controlled treatmentenergy parameters during the same or different treatment sessions. Forexample, in a scenario where fixed pulse widths are desired, thedisclosed technology initially determines whether that portion of the AChalf cycle above a minimum operating voltage is of sufficient durationto support the pulse width of the electrical energy used to pulse one ormore flash lamps in the dermatologic treatment device. If sufficientduration is found in the AC half cycle, the disclosed technologyoperates the dermatologic treatment device such that it drives the flashlamp to emit therapeutic levels of optical radiation during the periodof time in which the AC half cycle is at or above the minimum operatingvoltage. If the duration of the AC half cycle is insufficient to drivethe flash lamps as desired, an error condition is identified andreported to a user of the dermatologic treatment device.

Similarly, it may be advantageous to have some variability in the pulsewidths of individual pulses so long as the aggregate pulse width of thelight pulse sequence remains fixed. For example, the pulse width of thefirst pulse in the light pulse sequence may be somewhat shorter thanthose of the other pulses in that the first pulse is instantiated nearthe peak of an AC half cycle (substantially above the minimum operatingvoltage threshold) to facilitate triggering of the flash lamps withoutsacrificing the aggregate amount of therapeutic optical radiationapplied to a target skin treatment region by the light pulse sequence.

Alternatively, the disclosed technology can be configured in a moreflexible arrangement to provide variable pulse widths for individualpulses and/or for the light pulse sequence itself to dynamically accountfor sagging or “low line” conditions that may occur on the AC linesource, flash lamp degradation, varying skin types between skintreatment regions, or in other situations where operating or treatmentconditions are likely to vary. For example, and in order to operateproperly under the different high or low line conditions that may beencountered on an AC line source, the disclosed technology can includean AC line voltage detector that dynamically identifies that portion ofthe AC half cycle that exceeds a minimum operating voltage thresholdregardless of the specific condition of the electrical energy receivedvia an AC line source and then uses a processor to determine (viacomputation, table lookup, or otherwise) suitable pulse widths,inter-pulse delays, and/or pulse sequences that are capable of drivingone or more flash lamps to emit a therapeutically effective amount oflight energy to a skin region of interest.

Further, the disclosed technology can modify a minimum operating voltagethreshold in response to flash lamp degradation/aging characteristicssuch that the threshold is periodically increased to more readilyprovide greater electrical current thereby driving the flash lampsharder to provide a relatively consistent light output as the flashlamps age/degrade. This functionality can be facilitated by providing amemory that stores indicia pertaining to flash lamp aging/degradationcharacteristics along with other useful information (e.g., flash lampefficiency, maximum flash count, current flash count, initial amount ofelectrical current desired to drive the flash lamp to emit therapeuticlevels of optical radiation, a range of filtered wavelengths emitted bythe flash lamp, manufacturing batch information, indicia pertaining toother portions of an optical subsystem, and/or the like). In embodimentsincorporating such memory, it is desirable to include the flash lamp(s)and memory within a replaceable cartridge that can be readily insertedinto or removed from the dermatologic treatment device.

The disclosed technology can also vary the aggregate duration of thelight pulse sequence itself (e.g., by inserting greater inter-pulsedelays between individual pulses that are somewhat larger than multiplesof the duration of the applicable AC half cycle, or inserting moreindividual pulses) to accommodate different thermal relaxation times oftarget and nontarget tissue (e.g., lengthen the duration of inter-pulsedelays for darker skin types) and/or different dermatologic treatments.In some embodiments, a single light pulse sequence is applied to a skintreatment region during a treatment session, whereas in otherembodiments more than one light pulse sequence may be applied to part ofor all of the same skin treatment region during the treatment session.

The rate at which light pulse sequences are repeated during operation ofan illustrative dermatologic treatment device can be based at leastpartly on a momentary press of a button that results in the emission ofa single light pulse sequence (particularly useful when relativelysmall/limited regions of skin, e.g., between about 1-6 squarecentimeters, are to be spot treated) or on a momentary/sustained buttonpress when safety interlock components remain engaged for an extendedperiod of time resulting in the emission of repeating light pulsesequences (particularly useful when treating larger skin areas, e.g.,greater than about 6 square centimeters). The repeating light pulsesequences can, in some illustrative embodiments, occur at intervalsgreater than or equal to about 2.25 seconds, but preferably occur atshorter intervals such as between about 0.4-1 second and most preferablybetween about 0.5-0.75 second so that the therapeutic light energy canbe applied to adjacent skin treatment regions in a gliding fashion.

In brief overview, and with reference now to FIG. 1, at least someaspects of the disclosed technology can be embodied within anillustrative dermatologic treatment device 100 having a base 102 and ahand piece 104 interconnected by a flexible cable 106 preferably ofabout 5 feet or more in length. The device 100 also includes a powercable (not shown) interconnecting the base 102 with an AC line source(not shown). The device 100 is preferably sized to facilitate easystorage and transport in an end user environment (e.g., within a user'shome, a hotel room, or the like) and in one illustrative embodimentexhibits dimensions of less than about 9.5 inches in length, less thanabout 6.5 inches in width, and less than about 3.5 inches in height (orless than about 6 inches in aggregate height when the hand piece 104 isinserted into its cradle 110 on the base 102).

The housing of the base 102 is preferably made of a plastic material andencloses a switching power supply (discussed more fully below) suitablefor driving one or more flash lamps 112 in the hand piece 104 to emit adesired therapeutic light profile, as well as a user interface 108providing a user with status information (e.g., normal/error operatingconditions, indicia of remaining flashes, operating modes, indiciapertaining to the suitability of the device 100 for a user's skin type,or the like), as well as control features that enable or facilitatecontrol and operation of the device 100 (e.g., power level settings,operating mode selector, skin type detector 111, or the like).

The housing of the hand piece 104 is also preferably made of a plasticmaterial and encloses a cooling system (e.g., a variable-speed fan),temperature measurement components, user interface components (e.g.,flash initiation button 113), safety interlock components (e.g.,capacitive or mechanical skin contacting elements), an optical system(including, for example, one or more flash lamps 112, a curved, angular,or flat specular/diffusive reflector, an optical waveguide 105, and/oran optically transparent window), and/or the like. Although, the handpiece 104 can be configured such that it is not serviceable by an enduser, it is preferable to configure the hand piece 104 such that itshandle 114, replaceable light cartridge 116, and/or nose cap 118 can beseparated to facilitate periodic maintenance and repair. The handle 114preferably includes the cooling system, temperature measurementcomponents, and user interface components. The replaceable lightcartridge 116 preferably includes one or more flash lamps 112 (which maycontain particular reflective coatings thereon to filter out undesiredwavelengths), a reflector, and a memory (not shown) storing one morecharacteristics of the flash lamps 112. The nose cap 118 preferablyincludes the optical waveguide 105 (e.g., a substantially rectangular,hollow and specular light pipe preferably having a silver coating and alength of at least about 15 millimeters), optically transparent window(which may contain reflective coatings thereon), and safety interlockcomponents. In some embodiments, the components within the replaceablelight cartridge 116 can be incorporated into and be an integral part ofthe nose cap 118, such that the integrated nose cap serves as a singleuser replaceable component, rather than having separately-replaceablelight cartridges and nose caps.

During a dermatologic treatment session, the portion of the front,exterior housing of the nose cap 118 through which optical radiation ispassed is positioned substantially against the skin such that the skincontact elements detect the proximity of the housing to the skintreatment region of interest and safely enable operation of the device100. The light emitted by the flash lamp(s) 112 is filtered (passingwavelengths, for example, greater than about 600 nanometers, andpreferably greater than 650 nanometers) and conveyed through theoptically transparent window of the nose cap 118 so that it impinges onthe skin treatment region. Operation of the flash lamp(s) 112 in a pulsestate generates a significant amount of heat that needs to be dissipatedby the cooling system. Unfortunately, cost-effective, air-cooled devices100 suitable for the consumer market are not very efficient at removingthis heat and thus it is possible that the window in the nose cap mayreach a temperature that exceeds a threshold suitable for placementagainst a skin surface. Accordingly, air-cooled, dermatologic treatmentdevices 100 directed at the consumer market should either be operated ina manner that prevents overheating if the window is placed in contactwith the skin (e.g., reduce the flash rate of the flash lamps 112 byincreasing the time period between successive light pulse sequences sothat the cooling system has sufficient time to cool the window), recessthe window within the housing of the nose cap 118 (by at least, forexample, 4 millimeters, for a window of about 2 square centimeters) sothat the window does not come into contact with the skin during atreatment session, or provide a configuration that insulates the windowcontacting the skin from heat sources (e.g., the flash lamp 112 and/ormetallic light pipe 105).

In this last scenario, the window can be configured as a double panewindow with a sealed space between the two panes. This sealed space canenclose a partial vacuum, a gas such as xenon, or just air. The innerpane closest to the flash lamp(s) 112 preferably includes reflectivecoatings to filter out at least some undesirable wavelengths (e.g.,wavelengths below about 600 nanometers and/or above 1200 nanometers, fora hair removal/reduction dermatologic treatment) and is made ofborosilicate with a substantial hydroxyl component (e.g., greater thanabout 100 parts per million), whereas the outer pane designed forplacement substantially against the skin is preferably made of aspecialized composition of fused quartz/silica exhibiting a relativelylow hydroxyl component (e.g., less than about 50 parts per million andpreferably less than or equal to about 5 parts per million). In thismanner the relatively high hydroxyl composition of the inner pane itselfsupplements the filtration capabilities of the reflective coatingsthereon by absorbing some of the undesirable infrared emissions above2000 nanometers, while enabling any remaining low-level infraredemissions (between about 2000-4000 nanometers or higher) to pass throughthe outer pane substantially unimpeded and without unduly raising thetemperature of the outer pane. The remaining undesirable infraredemissions that pass through the outer pane and onto the skin are at asignificantly reduced fluence and are not harmful to the skin and do nototherwise adversely impact the efficacy of the dermatologic treatment.Those skilled in the art will recognize that the number of panes in thewindow can be more than two and/or that the space between panes can beopen (i.e., not sealed on at least 2 sides) to provide for a flow ofcooling air, gas, or liquid to pass therebetween.

In addition to preventing overheating of the skin, air cooleddermatologic treatment devices 100 must further maintain the temperatureof its components within a safe operating range without allowingexcessive light leakage (e.g., more than about 3 joules) that maydetract from a user's experience when operating the device 100. One ormore temperature sensors within the hand piece 104 and/or base 102 cangenerate signals indicative of excessive or near-excessive temperatureswhich can be mitigated by, for example, entering a cool-down mode inwhich the device 100 is prevented from driving its flash lamp(s) 112into a pulse state until a predetermined safety temperature is achieved,increasing the speed of the fan in the hand piece 104 and/or base 102,and/or reducing the rate at which light pulse sequences are repeated.

Judicious selection in the amount, orientation, location, andconfiguration of air inlet/outlet vents 120/122 in the hand piece 104can be made to ensure a desired airflow while concurrently preventingexcessive light leakage. For example, air inlet vents 120 can bepositioned on the nosecap 118 of the hand piece 104 with air outletvents 122 positioned substantially about the cable end of the hand piece104, thereby venting relatively hot exhaust air in a direction away fromthe skin treatment region. At least some of the vents that are morelikely to be subjected to light energy that has undesirably leaked outof the electrode ends of the flash lamp(s) 112 and/or out of the gapbetween the flash lamp 112 and waveguide 105 during operation of thedevice 100 are preferably configured to enable the passage of coolingair while concurrently reducing or substantially eliminating thetransmission of this leaked light energy outside of the hand piece 104using, for example, louvered or herringbone shaped vents. The vents canbe made of a reflective material (e.g., white teflon, aluminum, etc.) toreflect at least some of the leaked light back into the interior of thehand piece 104 or can be made of an absorptive material (e.g., pigmentedplastic) such that at least a substantial amount of the leaked lightimpinging on the vent is absorbed. Alternatively or in combination,vents exhibiting such louvered, herringboned, or other suitably shapedconfiguration can form part of the replaceable cartridge 116 so as tosubstantially trap the leaked light before it exits the cartridge. Thebenefits of incorporating such vents into the replaceable cartridge 116include reducing the amount of heat transmitted to other hand pieceelements due to their absorption of the leaked light and, in the casewhere the vent is made of a reflective material, redirect at least someof the leaked light back into the desired optical path such that theoverall fluence on the skin treatment region is increased.

FIGS. 2A-2G provide various perspective views of an illustrativereplaceable light cartridge 116 with dual flash lamps 112 that can beused in the dermatologic treatment device 100, while FIGS. 3A-3E provideanalogous views of an illustrative replaceable light cartridge 116 witha single flash lamp 112. More particularly, FIGS. 2A-2B and 3A-3B depictthe front (i.e., light emitting side) housing of the cartridge 116 inwhich a substantially open area 202 is defined, corresponding to thelocation of the arc of the flash lamp(s), which enables transmission oflight energy substantially unimpeded into the adjacent optical waveguide105 (FIG. 1). The vent configuration of this illustrative embodimentenhances the structural support of the cartridge 116 and enables adesired air flow to pass therethrough, while concurrently preventing auser from touching potentially hot flash lamp(s) 112 in the vicinity oftheir electrodes.

The louvered vents 204 of FIG. 2F are further tailored to block (i.e.,reflect back and/or absorb) more of the light energy that undesirablyleaks out of the electrode ends of the flash lamp(s) 112 withoutsignificantly restricting the air flow passed over such flash lamp(s)112. Similarly, the herringbone shaped vents 206 of FIG. 2G are adaptedto block even more leaked light than the louvered vents of FIG. 2F,albeit by sacrificing some air flow. The louvered and herringbone vents204, 206 depicted in FIGS. 2F and 2G are shown in connection with a dualflash lamp configuration, but they can also be incorporated into thefront housings of replaceable light cartridges 116 having a single flashlamp 112 or more than two flash lamps 112. Although the louvered vents204 and herringbone vents 206 are depicted as running horizontally alongthe front housing of the replaceable light cartridge 116, they can beoriented vertically or at substantially any angle in the front housingwithout adversely affecting operation of the device 100. Further, thelouvered and herringbone vents 204, 206 can include more such ventsstacked one in front of the other in the same or differentalignment/configuration to thereby create a labyrinth that substantiallyimpedes the passage of leaked light without unduly sacrificing air flownecessary to cool the flash lamp(s) 112 and other elements of thereplaceable cartridge 116. Light blocking vents that permit passage of adesired air flow can also be configured in a variety of other shapes andconfigurations, such as undulating, mesh, hexagonal, or honeycombedconfigurations or the like.

FIGS. 2C-2E and 3C-3E illustrate an exemplary housing in the rear sideof the replaceable cartridge 116 shown in FIGS. 2A-2B and 3A-3B. Thisportion of the housing defines two substantially open regions 210 thatfacilitate passage of cooling air over the flash lamp(s) and other partsof the cartridge 116. The substantially centered region 212 of the rearhousing, between the open regions 210, positions a reflector 214 (FIG.2G) in fixed proximity to the flash lamp(s). Although this reflector 214is depicted as flat, it can assume a variety of curved, angular,dimpled, or other shapes/configurations and can be made of a diffusiveor specular material. The rear housing also includes a trigger pin 216that is used to convey an electrical trigger pulse sufficient to ionizethe gas in the flash lamp(s) 112, anode and cathode pins 218 that conveyan electric current sufficient to maintain a simmer state and pulsestate in the flash lamp(s) 112, and input-output pins 220 of a memory(not shown) that stores flash lamp characterization data useful inoperating the flash lamp(s) 112 and device 100 (particularly as thelight output of the flash lamp(s) 112 degrades over time). Those skilledin the art will recognize that the particular placement of these pins216-220 are merely illustrative and that a variety of pin placements arepossible; for example, the anode and cathode pins 218 can be located inproximity to each other as shown in FIGS. 2C, 2E, 3C, and 3E or can belocated on opposite sides of the rear housing as shown in FIGS. 2D and3D.

In more detail, and with reference now to FIGS. 1 and 4, anillustrative, flash lamp-based dermatologic treatment device 100 made inaccordance with the disclosed technology includes a user interface 108that enables a user to interact with the device 100, an optical system404 that generates and conveys a therapeutic amount of optical radiationto a skin treatment region, a cooling system 406 that maintainsoperation of the device 100 within desired operating temperatures, atemperature measurement system 408 that detects over-temperatureconditions, a safety interlock system 410 that prevents inadvertentemissions of optical radiation and other hazardous occurrences, a flashlamp characterization system 412 that serves as a basis for dynamicallyadjusting electrical operating parameters during operation of the device100 in response to flash lamp or other optical system 406 properties,and a switching power supply 414 that draws electrical energy from an ACline source 426 and conditions such energy to drive the optical system404 in a desired manner.

The user interface 108 presents a user of the device 100 with selectionsconcerning the desired operation of the device 100 (e.g., one or morepower level settings that concurrently affect both the efficacy of thedermatologic treatment and the user's sensation experienced during theperformance of such treatment; settings that operate the device 100 in apulse mode where a single light pulse sequence is emitted or in strobemode where a plurality of light pulse sequences are emitted in apredetermined sequential manner; and/or the like), as well as with theability to initiate a dermatologic treatment (e.g., the flash initiationbutton 113 of FIG. 1), and various visual, auditory, haptic, or othersensory feedback mechanisms that inform the user of operating or errorconditions (e.g., whether the device 100 is suitable for treating aparticular user's skin type, whether a maximum flash count has beenexceeded, whether a replaceable light cartridge 116 (FIG. 1) or nosecap118 are properly installed, whether an over-temperature condition hasoccurred, whether a power supply failure has occurred, and/or the like).In performing these functions, the user interface 108 interacts,directly or indirectly, with a control circuit 424 of the switchingpower supply 414 as more particularly described below.

The optical system 404 preferably includes one or more flash lamps 112,a reflector, a filter, and an optical waveguide 105, all containedwithin a handheld housing. As previously mentioned, the flash lamp(s)112 and reflector (preferably mounted within about 1 millimeter of theflash lamps 112) are further contained within a replaceable lightcartridge 116 that is inserted into the hand piece 104, while the filterand optical waveguide 105 are contained within the housing of thenosecap 118 of the hand piece 104. In some embodiments, one or morereflective coatings can be applied directly to the exterior of the flashlamp(s) 112 to provide the desired wavelength filtration and/or toprevent undesirable light leakage at the electrode ends of the flashlamp(s) 112. Although these directly-applied coatings increase the costand manufacturing complexity of the optical system 404, the overalloptical emissions through the arc portion of the flash lamp(s) 112 areincreased due to light recycling and light reclamation (i.e., the lightwhich would otherwise have leaked out of the electrode ends of the flashlamp(s) 112 is reflected back into the desired optical path), therebyenabling a smaller quantity of electrical current to provide a givenamount optical energy. In other embodiments, the reflective coatings areincorporated in a separate filter so that the additional heat generatedas a result of any filtration does not further increase the thermal loadof the flash lamp(s) 112—particularly beneficial when the flash lamps112 are made of borosilicate rather than quartz or sapphire. Further,the optical waveguide 105 can be made of a solid, optically transparentmaterial such as PMMA or can be configured as hollow, specular lightpipe with interior reflective walls coated with silver (exhibiting, forexample, a greater than 98% reflectance for wavelengths between about600-1200 nanometers). When configured as a hollow light pipe, theoptical waveguide 105 preferably includes parallel reflecting walls tominimize back reflections, as well as cut-out sections in two of itsside walls so that the waveguide substantially encloses the arc portionof the flash lamp 112 (exemplary spacing between the waveguide 105 andenvelope of the flash lamp(s) is preferably about 0.5 millimeters) whilefacilitating cooling of the electrode ends of the flash lamp 112.

The cooling system 406 includes at least one fan together withappropriately sized and positioned vents (e.g., as shown in FIGS. 1-3)to provide sufficient cooling for the device 100 over its intendedoperating range. Although a fan can be provided within the housing ofthe base 102 in order to cool the switching power supply 414, it ispreferable to design the device 100 so that the switching power supply414 is cooled passively and that the fan be primarily dedicated tocooling the flash lamps 112 and other elements in the hand piece 104.

In such preferred configurations, the fan can be configured to eitherblow air onto the flash lamps 112 or suck air over the flash lamps 112.The fan can also be a single speed fan that operates at full speed uponpower-up of the device 100 or a variable speed fan that increases itsair flow based on temperature measurements within the hand piece 104.The variable speed fan is preferred in situations where a relativelysmall region of skin is to be treated (e.g., up to about 60 squarecentimeters of a skin surface) since it results in relatively quietoperation of the device 100 that is more readily tolerated by its user.As the size of the treatment region increases, and the temperaturewithin the hand piece 104 increases, the fan can be driven at a higherspeed to maintain the safe operation of the device 100. For example, thefan can be operated at a relatively high speed when the temperature inthe hand piece 104 exceeds about 40 degrees Celsius and at a slowerspeed when the temperature drops below about 35 degrees Celsius.

Further, the optical system 404 can be configured to facilitate coolingof the hand piece 104 without losing an excessive amount of energy dueto light leakage. For example, a first end of the optical waveguide 105can be positioned about 1 millimeter from the reflector and a second endcan be positioned about 1 millimeter from an output window, therebyenabling some air flow to cool a surface of the window, as well as coolthe interior of the hollow waveguide 105 and the reflector and arcportion of the flash lamp(s) 112, albeit with some loss in light energy.In one embodiment, the distance between one or more such elements can bemade variable based on whether the flash lamp(s) 112 is being driven ina pulse state at that moment. For example, the distance between theoptical waveguide 105 and the reflector and/or window can be decreased(e.g., to about 0.5 millimeters) or completely eliminated when the flashlamp(s) 112 is driven into a pulse state and otherwise remain at theiroriginal 1 millimeter positions, thereby minimizing light leakage duringintense light emissions (e.g., during emission of a single light pulseor during emission of a light pulse sequence) and facilitating coolingduring simmer or other operating states.

The temperature measurement system 408 includes one or more temperaturesensors that can be positioned in the base 102 to measure the operatingtemperature of the switching power supply 414 and/or in the hand piece104 to measure the operating temperature of the optical system 404. Whenpositioned within the hand piece 104, the temperature sensor(s) ispreferably located in the path of the exhaust air emitted by the coolingsystem 406 and that is further shielded from any substantial lightemissions from the optical system 404. Upon detecting anover-temperature condition (e.g., at or above 50 degrees Celsius), thetemperature measurement system 408 can generate a signal that causes thedevice 100 to either enter a cool down mode in which the switching powersupply 414 is inhibited from driving the flash lamp(s) 112 into a pulsestate, increase a time interval between successive light pulsesequences, and/or otherwise suspend normal operation until the measuredtemperature falls within a safe temperature range, which would likely beseveral degrees Celsius below the over-temperature threshold (e.g., 45degrees Celsius).

The safety interlock system 410 detects whether the device 100 isproperly positioned when treating a skin treatment region and whether itis properly assembled to prevent inadvertent exposure to hazardouselectrical energy within the hand piece 104. For example, the safetyinterlock system 410 can include capacitive, optical, mechanical,bioimpedance, and/or other types of sensors in the vicinity of thatportion of the nosecap 118 of the device 100 that is intended forplacement substantially on or adjacent to the skin surface of a skinregion to be treated. When a gliding motion is desired during atreatment session, it is preferable to couple a plurality of mechanicalsensors to a frame forming part of the nosecap 118 that substantiallysurrounds the optical aperture of the device 100 (e.g., frame that holdsthe output window in desired position(s) within the optical path), whichfacilitates the gliding movement of the nosecap 118 when transitioningbetween adjacent skin treatment regions during a dermatologic treatment,rather than using individual sensors/plungers that are more amenable tostamping-type treatment movement and that are not as accommodating togliding treatment motions. In an embodiment where the mechanical sensoris incorporated at least partly into the frame holding the window, thedistance that such mechanical sensor is depressed preferably correspondsto the amount of decreased distance between the window and opticalwaveguide 105 as discussed above in connection with improving theoptical efficiency of the device 100 during the pulse state of the flashlamp(s) 112. The safety interlock system 410 can also include a resistor(or other identification means) within the nosecap 118 that provides thebasis for uniquely identifying authorized nosecaps and ensuring that anysuch nosecaps 118 are properly inserted into the handle 114 of the handpiece 104 before the switching power supply 414 applies any electricalenergy to the optical system 404, thereby ensuring proper operation ofthe device 100 and reducing the risk of shock and optical hazards to auser.

The flash lamp characterization system 412 is preferably incorporated,at least partly, into the replaceable light cartridge 116 and includes amemory 413 that stores one or more characteristics of the flash lamp(s)112 to ensure that the device 100 emits the desired amount of opticalradiation during a dermatologic treatment session. The memory 413 ispreferably a EEPROM element that provides non-volatile random memoryaccess to stored flash lamp characteristics, such as a maximum number offlashes available for the flash lamp(s) 112, a current flash count forsuch flash lamp(s) 112, a range of wavelengths emitted by the flashlamp(s) 112 (particularly useful when the flash lamp(s) 112 includefilter coatings on their exterior), an initial amount of electricalenergy desired for driving the flash lamp(s) 112 into a pulse state, afirst electrical compensation factor to adjust for reduced light outputfrom the flash lamp(s) 112 as a result of aging, a second electricalcompensation factor to adjust for the electrical-to-optical conversionefficiencies of particular flash lamp(s) 112 or flash lamp types, flashlamp 112 and cartridge manufacturing information (e.g., date, partnumber, etc.), an authorization code for the replaceable light cartridge116, and/or the like.

The switching power supply 414 includes an AC line voltage detector 416that detects locations within AC half cycles drawn from an AC linesource 426 that are sufficient to provide the requisite electricalenergy to drive the flash lamp(s) 112 to emit desirable levels oftherapeutic light energy, a trigger power circuit 420 that instantiatesionization of the gas within the flash lamp(s) 112, a pulse-drivecircuit 422 that provides the requisite electrical energy to drive theflash lamp(s) 112 to emit one or more desirable light pulse sequencesthat facilitate achievement of a desired dermatologic cosmetic effect ina skin treatment region, a simmer power circuit 418 that maintains theionization of the gas within the flash lamp(s) 112 with a low currentdensity between light pulses, and a control circuit 424 that controlsand/or otherwise interacts with circuits, systems, and elements of thedevice 100 during operation of the device 100.

The AC line voltage detector 416 compares voltage levels of theelectrical energy provided by the AC line source 426 against one or morereference voltages (reference voltages can be at a predetermined levelor dynamically generated by the control circuit 424) that is indicativeof a minimum operating voltage threshold. The AC line voltage detector416 generates a signal that is transmitted to the control circuit 424and is indicative of when the AC half cycle meets or exceeds the minimumoperating voltage threshold. For example, the duty cycle of this signalcan indicate when the minimum operating voltage threshold is met orexceeded by being “high” during the period of the AC half cycle that isat/above this threshold. Alternatively, the signal can be “low” duringthe period of the AC half cycle that is at/above the threshold and“high” only during transition periods between adjacent AC half cycleswhere the line voltage is below the threshold. Accordingly, the dutycycle or inverse of the duty cycle of the signal generated by the ACline voltage detector 416 is dynamically generated based on the thenexisting conditions of the AC line source 426 and provides timelyinformation to the control circuit 424, which is subsequently used totime flash lamp emissions during that portion of the AC half cycle inwhich sufficient electric current can be drawn from the AC line source426 to properly operate the flash lamp(s) 112 as desired. The device 100can be configured to perform such voltage comparisons upon initialpower-up and/or upon periodic intervals so as to dynamically determinechanges in the AC line source 426 that may be caused by sagging,spiking, or other power-related fluctuations that may affect operationof the device 100 and for which such operation can be dynamicallyadapted to compensate for such fluctuations. An illustrative circuit fora suitable AC line voltage detector 416 is provided in FIG. 16 and isfurther discussed below.

The trigger power circuit 420 is under the control of the controlcircuit 424 and includes a transformer that increases the input voltageof the electrical energy to about 6-10 kilovolts, which is of sufficientmagnitude to trigger/instantiate ionization of the gas within the flashlamp(s) 112. For example, the control circuit 424 can enable the triggerpower circuit 420 to instantiate ionization by applying a 10 kilovoltpulse of between about 200 nanoseconds-1 millisecond in duration toelectrically-conductive, optically transparent coatings on at least partof an exterior of the flash lamp(s) 112 to capacitively couple this highvoltage pulse into the flash lamp(s) 112 resulting in the ionization ofthe gas. In some embodiments, the input energy provided to the triggerpower circuit 420 is drawn substantially directly from the AC linesource 426. In another embodiment, the trigger power circuit 420 sharescomponents with the simmer power circuit 418 so that the inputelectrical energy is drawn substantially from the simmer power circuit418 and applied to trigger-dedicated components to generate the highvoltage pulse. An illustrative trigger power circuit 420 made inaccordance with such an embodiment is depicted in FIG. 14 and is morefully discussed below.

The pulse-drive circuit 422 is operated under the control of the controlcircuit 424 and includes a buck regulator that applies regulated, highdensity electrical current of, for example, between about 30-80 amps(more preferably between about 40-65 amps) to the electrodes of theflash lamp(s) 112 while the gas therein is ionized, resulting in intenselight emissions that are suitable to facilitate achievement of a desiredcosmetic effect in a skin treatment region. The regulated electricalcurrent supplied to the flash lamp(s) 112 exhibits substantially thesame profile as that desired for the light pulse sequences and is timedto coincide with that portion of the AC half cycle that is above aminimum operating voltage threshold as determined by the AC line voltagedetector 416. In this manner, sufficient peak electrical current can bedrawn from the AC line source 426 to support performance of the desireddermatologic treatment without unduly stressing external power circuitsor requiring expensive capacitive circuit components.

The simmer power circuit 418 is also operated under the control of thecontrol circuit 424 and includes transformer and capacitor elements thatapply a low current density (e.g., 50-100 milliamps) to the flashlamp(s) 112 between intense light pulse emissions. The transformer ofthe simmer power circuit 418 increases the input voltage from the ACline source 426 to about 750 volts for a dual flash lamp device (about375 volts for a single flash lamp device) and applies this “simmer”energy to the flash lamp(s) before, during, and/or after the flash lamppulse state. For example, in embodiments where components of the simmerpower circuit 418 and trigger power circuit 420 are shared, the simmerenergy is applied to the flash lamp(s) 112 in advance of the highvoltage pulse provided by the trigger circuit, since the combination ofthe simmer and trigger voltages is sufficient to ionize the gas in theflash lamp(s) 112. Following ionization, the simmer energy can beapplied at various times during operation of the device, such ascontinuously during individual light pulse sequences, during and betweenmultiple light pulse sequences, during the inter-pulse delay intervalsbetween individual pulses in a light pulse sequence, and/or the like.Those skilled in the art will recognize that a simmer power circuit 418is not a requirement for proper operation of the dermatologic treatmentdevice 100, but rather provides a mechanism to reduce the thermal andmechanical shock loads on the flash lamp(s). An illustrative simmerpower circuit 418 is depicted in FIG. 13 and is more fully discussedbelow.

An illustrative control circuit 424 includes a processor to monitor andcontrol operation of the device 100, along with current regulationcircuitry to support operation of the pulse-drive circuit 422, simmercontrol circuitry to support operation of the simmer power circuit 418,trigger control circuitry to support operation of the trigger powercircuit 420, and pulse duration protection circuitry to provide a safetymechanism that disables the device 100 in the event a component failurewithin the switching power supply 414 inadvertently results in excessiveelectrical energy being provided to the flash lamp(s) 112 that couldresult in undesirable light emissions therefrom. In brief overview, thecontrol circuit 424 determines whether the device 100 is properlyconfigured and capable of operating as designed when connected to aparticular AC line source 426, and further operates the device 100according to one or more user preferences to provide a therapeuticallyeffective amount of optical radiation to one or more skin treatmentregions during a dermatologic treatment session. The processor of thecontrol circuit 424 executes algorithms and operates on data, variables,and other run-time components that are at least partially stored withinsuch processor's memory and can best be described with reference to theillustrative methodology depicted in FIG. 5. Supporting hardwareelements of an illustrative control circuit 424 are best understood withreference to FIG. 16 and its accompanying description below.

In one illustrative operation, and with reference now also to FIG. 5, anexemplary dermatologic treatment device 100, made and operated inaccordance with at least some aspects of the disclosed technology,includes a control circuit 424 with a processor (e.g., PIC16F883microcontroller, a product of Microchip Technology, Inc.) that executesstored instructions in a preemptive multitasking manner where nontime-critical tasks are run in a state machine in the background andtime critical tasks are run under interrupt priority in the foreground.Upon powering up, the processor initializes its internal clock,configures and initializes its input/output ports, initializes systemdrivers, initializes state values, enables interrupts, sets the state oflight emitting diodes and other elements in the user interface 108, andotherwise initializes the device 100 (502).

The processor then performs self tests on the device 100 to ascertainwhether it is in proper working condition (504). For example, theprocessor can evaluate signals or other indicia from i) the coolingsystem 406 to ensure that its fan is operating at the proper speed, ii)the temperature measurement system 408 to ensure that the device 100 cansafely operate at its current temperature, iii) pulse durationprotection circuitry in the control circuit 424 that determines whetherone or more conditions exist within the pulse-drive circuit 422 or otherelements of the switching power supply 414 that might result in drivingthe optical system 404 with excessive electrical energy that could behazardous to a user and/or confirming that safety circuitry designed toprevent such hazardous conditions in the event of a hardware failure isoperating properly, iv) the flash lamp characterization system 412 toensure that the replaceable light cartridge 116 and flash lamp(s) 112are authorized by the manufacturer of the device 100 and shouldtherefore operate as intended and are properly installed within thedevice 100, v) the nosecap 118 to ensure that it is also authorized bythe manufacturer and contains proper elements of the optical system 404for a particular dermatologic treatment and is also properly installedwithin the device 100, and/or vi) the safety interlock system 410 toensure that the device 100 is properly assembled/configured and thatsafety elements are in proper working condition such that a user is notexposed to hazardous electrical or optical conditions (which may occur,for example, when failed skin contact sensors are stuck in an engagedposition thereby erroneously signifying that it is safe to emit intenselight pulse emissions from the optical system 404).

The processor of the control circuit 424 determines the characteristics(e.g., frequency, high or low line conditions, sagging conditions, etc.)of the AC energy provided by the AC line source 426 by, for example,receiving one or more signals from the AC line voltage detector 416representative of such characteristics (506). In one illustrativeembodiment, the signal generated by such detector 416 includes at leasttwo pulses, where the rising edge of the first pulse is substantiallyaligned with that portion of a first AC half cycle that is at theminimum operating voltage threshold following the peak of the half cycleand the falling edge of the first pulse is substantially aligned withthat portion of the next adjacent, rectified AC half cycle (i.e., thesecond AC half cycle) that is at the minimum operating voltage thresholdprior to the peak of that half cycle. Similarly, the rising edge of asecond pulse is aligned with the minimum operating voltage thresholdposition on the decreasing slope of the second half cycle and thefalling edge of the second pulse is aligned with the minimum operatingvoltage threshold position on the increasing slope of the third AC halfcycle, and so forth. The time difference between the rising edges of thefirst and second pulses is indicative of the frequency of the AC energyprovided by the AC line source 426, whereas the pulse width of eachpulse (i.e., the time difference between the rising and falling edges ofa given pulse) is indicative of high-line, low-line, or sagging powerconditions. For example, a low-line condition on a 50 Hz AC line, wouldresult in a 10 millisecond time difference between rising edges inadjacent pulses (8.3 millisecond time difference for a 60 Hz AC line)and with each pulse duration being somewhat longer than normal orhigh-line conditions. In ascertaining, the characteristics of the ACline, the processor of the control circuit 424 preferably averages theabove time differences and pulse durations for multiple adjacent pulses(e.g., 32 adjacent pulses) to ensure that any outlier or erroneousmeasurements do not unduly affect the power and operational settings ofthe device 100.

The processor also accesses maximum flash count and current flash countinformation stored within a memory 413 of the flash lampcharacterization system 412 to determine whether the flash lamp(s) 112is/are still operable (i.e., have not yet exceeded the maximum flashcount) (508). If the flash lamp(s) 112 is/are not operable, theprocessor causes the user interface 108 to prompt a user of the device100 to replace such flash lamps (510). For example, the user interfacecan flash one or more light emitting diodes, beep, and/or otherwiseindicate to the user that a replaceable light cartridge 116 containingsuch flash lamp(s) 112 needs to be replaced. The user interface 108 canalso make the user aware of when the current flash count is approachingthe maximum flash count so that the user can purchase anotherreplaceable light cartridge in advance of end-of-life on the installedcartridge. If the flash lamp(s) 112 is/are operable, the processorevaluates signals or other indicia of the user interface 108 to detectselections made by or on behalf of a user of the device 100, such asdermatologic treatment type, power level settings, strobe versus pulseoperating modes, skin/hair type settings, and/or the like (512).

The processor determines the power compensation and pulse waveformsettings that are desirable for a particular dermatologic treatmentbased at least partly on the user selections, characteristics of the ACenergy provided by the AC line source 426, and flash lampcharacteristics (514). More particularly, the processor uses informationpertaining to the dermatologic treatment type, power level settings,and/or skin/hair type settings to determine (based on computation and/ordata structure lookup) the fluence, pulse durations, and/orinter-pulse/inter-sequence delays of one or more light pulses and/orlight pulse sequences that are desirable for facilitating achievement ofthe desired dermatologic treatment. The processor further uses the ACline and flash lamp characteristics to determine the correspondingparameters of the electrical energy that is to be supplied by theswitching power supply 414 to the optical system 404 to achieve thedesired light profile. For example, sagging or low-line AC inputconditions that exhibit periods of time in which voltage levels are lowrelative to nominal voltages require the application of higher electriccurrents to compensate for such low voltages and maintain asubstantially constant power in the flash lamp(s) 112 and may alsoresult in shorter pulse durations (in variable pulse embodiments) foreach electrical pulse in the sequence of electrical pulses (whichcorrespond to the light pulses in the light pulse sequence). Similarly,high-line AC input conditions provide higher voltages requiring lowercurrents to compensate for such high voltages in order to maintain asubstantially constant power in the flash lamps(s) 112. Further, theaging and electric-to-light conversion characteristics of the flashlamp(s) 112 may necessitate additional modifications to the electriccurrent provided to such flash lamp(s) 112. For example, the flash lampaging/degradation characteristics for the flash lamp(s), which arestored in the memory 413 of the flash lamp characterization system 412preferably include a predetermined percentage of light loss per somenumber of light pulses or light pulse sequences (e.g., a 5% loss inoptical fluence for every 1000 light pulse sequences) that can be usedto compute an electrical compensation value that increases the electriccurrent to the flash lamp(s) 112 by an amount sufficient to compensatefor this degradation, thereby achieving the desired, and substantiallystable, optical fluence during the same or subsequent dermatologictreatment session. Similarly, the particular flash lamp(s) 112 installedwithin a replaceable light cartridge 116 may vary from cartridge tocartridge such that there may be a difference in the electric-to-opticalconversion efficiency in such flash lamps 112, in which case acompensation factor stored within the memory 413 of the flash lampcharacterization system 412 provides a mechanism by which the processorcan adjust the electrical output of the switching power supply 414 toaccommodate the desired light pulse sequence during the dermatologictreatment.

When a user of the device 100 presses the flash initiation button 113 ofthe user interface 108, the processor of the control circuit 424 detectssuch selection and, preferably while the button 113 is still beingpressed, monitors the safety interlock system 410 to detect a signaltherefrom indicative of when the skin contact sensors of the safetyinterlock system 410 are engaged, signifying that at least the portionof the hand piece 104 from which optical radiation is to be emitted issubstantially in contact with or substantially surrounds the skin regionto be treated (516). The processor then preferably accesses thetemperature measurement system 408 and determines whether thetemperature within the hand piece 104 and/or other locations within thedevice 100 are within a manageable temperature operating range (518). Ifthe temperature is below a first temperature threshold signifying a safeoperating temperature, the processor can instruct simmer controlcircuitry within the control circuit 424 to enable the simmer powercircuit 418 (520). If the temperature is within the manageabletemperature operating range, between the first temperature threshold anda second temperature threshold, the processor can optionally decidewhether to modify operation of the cooling system 406 (e.g., increasethe speed of a variable speed fan within the hand piece 104 or elsewherein the device 100) and/or modify parameters associated with the lightpulse sequences and/or associated electrical pulses (e.g., increase thetime interval between successive light pulse sequences thereby at leasttemporarily decreasing the overall flash rate of the device 100) so thatthe temperature within the device stays within desired temperaturelimits during and/or immediately following the next light pulse sequence(522). If the measured temperature exceeds the higher of the twotemperature thresholds, signifying an unsafe operating condition, theprocessor can issue a signal to the switching power supply 414 thatpowers down the device 100 (524).

In one embodiment, it takes about 125 milliseconds after the simmerpower circuit 418 is enabled for the circuit 418 to reach its fulloutput voltage (of about 750 volts for a dual flash lamp device), inwhich case the processor uses its internal clock to measure this timeperiod and suspends any further power-related activities until this timeperiod lapses. Once the simmer power circuit 418 achieves its desiredoutput voltage, the processor can optionally check whether the safetyinterlocks remain engaged (526) or proceed with sending a signal totrigger control circuitry of the control circuit 424 to enable thetrigger power circuit 420 (528). If the processor detects that thesafety interlocks are no longer engaged, it can issue a signal to thesimmer control circuitry that disables the simmer power circuit 418(530).

As previously mentioned, it is preferable that the simmer power circuit418 and trigger power circuit 420 share components such that the simmeroutput voltage is added/transformed to the trigger power voltage (e.g.,between about 6-10 kilovolts) to reach a sufficient magnitude inaggregate to trigger/instantiate ionization of the gas within the flashlamp(s) 112, which marks the beginning of the flash lamp's simmer state(532). Following ionization, the simmer state can be maintained bycontinuing to apply between about 50-100 milliamps of electric currentto the flash lamp(s) from the simmer power circuit 418. The processorcan then optionally check whether the safety interlocks remain engaged(534) or proceed by sending a signal to current regulator circuitry ofthe control circuit 424 to enable the pulse-drive circuit 422 (536). Ifthe safety interlocks were no longer engaged, the processor can issue asignal to the simmer control circuitry that disables the simmer powercircuit 418, which would effectively terminate the simmer state of theflash lamp(s) 112.

The processor issues signals and provides reference voltages to thecurrent regulator circuitry that drive the pulse-drive circuit 422 ofthe switching power supply 414 to generate pulses of electrical energy,which substantially mirror the shape and other attributes of the lightpulse sequences, and that energize the flash lamp(s) 112 while in asimmer state to emit intense pulsed light emissions during the lamp'spulse state (538). As previously discussed, the electrical energyprovided by the pulse-drive circuit 422 to energize the flash lamp(s)112 from a simmer state into their pulse state is drawn substantiallyfrom the AC line source 426 during periods within the AC half cycle thatare above a minimum operating voltage threshold. This portion of the AChalf cycle is also capable of providing the desired peak current levelsnecessary to drive the flash lamp(s) during their pulse state withoutdrawing any substantial energy from any charged capacitors. The shape(e.g., pulse duration, inter-pulse delay intervals, degree of electricalcurrent oscillation about a nominal current value and within upper andlower limits) and size (e.g., peak and average electrical current) ofthe electrical pulses and sequences of electrical pulses generated bythe pulse-drive circuit 422 can be maintained within a desired pulseprofile determined by the processor. More particularly, the processorissues signals to the current regulator circuitry that selectivelyenable a field-effect transistor or other power switching element in thebuck regulator circuitry of the switching power supply 414 to conductelectrical energy to the flash lamp(s) 112. Since many dermatologictreatments are preferably performed with substantially square lightprofiles, the processor can control the power switching element toselectively conduct or inhibit electrical energy transmissions, suchthat the electrical energy provided to the flash lamp(s) oscillates(e.g., at between a 50-100 kilohertz rate and more preferably at aboutan 80 kilohertz rate) about a desired current level and within upper andlower current limits so that the current is substantially regulated. Theprocessor enables or disables the power switching element based at leastpartly on the amount of current that passes through the flash lamp(s)112 at a given moment during the pulse state (determined via, forexample, a current sensing resistor), which affects the magnitude of thecurrent oscillation about the desired level (e.g., between about 35-80amps, and more preferably between about 47-65 amps+/−10 amps), and onthe duty cycle or inverse of the duty cycle of the signal generated bythe AC line voltage detector during periods within the AC half cyclesthat are at or above the minimum operating voltage thresholds (used totransition between pulse and simmer states of the flash lamp(s) 112during and after electrical/light pulse sequences).

The control circuit 424 of the switching power supply 414 can detect oneor more critical faults that may occur as a result of a hardware orsoftware malfunction during or after emission of a light pulse sequence(540). For example, a failure of the power switching element that shortsthe element into a continuously conducting state could result inexcessive, unregulated electrical energy driving the flash lamp(s),which could result in undesirable light emissions during the lamp'spulse state. If a critical fault (i.e., unrecoverable fault condition)occurs, the processor, pulse duration protection circuitry and/or othercircuitry within the control circuit 424 can use an IGBT or otherswitching element to permanently or temporarily disable the device 100(542). In one embodiment, the device 100 is permanently disabled after acritical fault condition repeats itself several times within a giventime period. If a critical fault condition does not occur and the lightpulse sequence is successfully emitted, then the processor can instructthe control circuit 424 to disable the simmer, trigger, and pulse-drivecircuits 418-422 (544) and to update the current flash count or otherflash lamp characteristics stored in the memory 413 of the flash lampcharacterization system 412 (546) in preparation for subsequentoperations of the device 100.

It is important to note that the illustrative methodology depicted inFIG. 5 and described above can be modified in various ways withoutmaterially departing from the benefits of the disclosed technology. Byway of non-limiting example, the methodology described in blocks 502-518can be combined in whole or in part or performed in different sequences;determinations of when safety interlocks are engaged need not occur inthe time period beginning with the simmer state and ending upontermination of the pulse state of the flash lamp(s) 112; the simmerstate can be completely avoided by operating the flash lamp(s) in theirpulse state substantially immediately following emission of the triggerpulse; and/or the simmer state of the flash lamp(s) can continue beyondtermination of the pulse state and thus during the period of timebetween adjacent light pulse sequences.

With reference now also to FIGS. 6-12, illustrative electrical, optical,and thermal waveforms are shown, which may be encountered in anillustrative dermatologic treatment session directed to temporary hairremoval using an exemplary dermatologic treatment device 100 made andoperated in accordance with at least some aspects of the disclosedtechnology. More particularly, FIG. 6 depicts a full wave rectified ACpower signal (with a 50 Hz frequency and a corresponding 10 millisecondperiod) exhibiting either a high-line condition 602 or a low-linecondition 604. The nominal AC voltage condition is not shown so as toavoid unduly cluttering the figure, but those skilled in the artrecognize that such nominal voltage waveform would be located betweenthe high and low-line waveforms 602, 604. An illustrative minimumoperating voltage threshold 606 is also depicted and the intersection ofsuch threshold 606 with the high-line waveforms 602 shows that theduration of that portion of the AC half cycle above the threshold 606 isgreater than the corresponding duration of the low-line waveform 604.Accordingly, high-line AC conditions can accommodate longer electricaland light pulse widths and lower peak currents required for a particulardermatologic treatment than low-line AC conditions.

FIG. 7 depicts an illustrative signal 702 that may be formed by the ACline voltage detector 416 to assist the processor of the control circuit424 in its determination of AC line frequency and durations within theAC half cycles that meet or exceed the minimum operating voltagethreshold 606. In the illustrated embodiment, each pulse in the signal702 is indicative of when the voltages of the AC half cycles are belowthe minimum operating voltage threshold 606. Note that the duration ofsuch pulses are shorter for high-line AC conditions than for low-line ACconditions, in which case the inverse of the depicted duty cycleidentifies that portion of the AC half cycle that can provide sufficientelectrical energy to drive the flash lamp(s) 112 (from a simmer stateinto a pulse state) of the dermatologic treatment device 100 during atreatment session without drawing any substantial electrical energy froma charged capacitor. In another embodiment, the AC line voltage detector416 can generate a signal that is the inverse of the depicted signal 702in which case its duty cycle would substantially directly reflect thatportion of the AC half cycles capable of driving the flash lamp(s) 112in the disclosed manner.

FIG. 8 provides a signal diagram of an illustrative voltage waveform 802that may be applied across dual flash lamps of a dermatologic treatmentdevice during a temporary hair removal treatment session in which an AChigh-line condition exists. In this embodiment, the simmer power circuit418 initially applies about 750 volts to the flash lamps, which issubsequently combined with the voltage provided by the trigger powercircuit 420 to achieve a 10 kilovolt trigger signal in aggregate that issufficient to capacitively trigger/instantiate ionization of the gas inthe flash lamps. The control circuit 424 then causes the pulse-drivecircuit 422 to convey voltage pulses to the flash lamps substantiallyduring the duration of the AC half cycle above the minimum operatingvoltage threshold 606 (in this case, for a duration of about 7milliseconds), where such voltage pulses are separated by about 3milliseconds during which a simmer voltage is maintained across theflash lamps. As shown the voltage pulses can exhibit a substantiallysquare profile with an oscillation of about +/−25 volts about theaverage voltage of 100 volts.

FIG. 9 provides a signal diagram of an illustrative electric currentwaveform 902 corresponding to the voltage waveform 802 of FIG. 8. Inthis embodiment, a low level current of about 100 milliamps begins toflow across the flash lamp(s) upon instantiation of ionization of thegas in the flash lamp(s) and such low level current continues to flow inthe inter-pulse period to ensure that the gas remains ionized at leastuntil the corresponding light pulse sequence is completed. During thepulse state of the flash lamp(s), the current increases to about 50 ampsand is maintained within about +/−10 amps of that level as a result ofthe 80 kilohertz switching action of the pulse-drive circuit 422 aspreviously described. In a related embodiment that further reducesthermal and mechanical shocks to the flash lamp(s), the aggregate pulsewidth of the current waveform 902 can be extended (e.g., to betweenabout 50-250 ms, preferably between about 60-130 ms, and most preferablyto about 110 ms in total) such that additional regulated current at amoderate intensity level (e.g., between about 1-25 amps, preferablybetween about 1-15 amps) is applied continuously to the flash lamp(s)during a period following ionization of the flash lamp(s) and up to theintense light emissions occurring at the 50 amp current level. Thismoderate current level not only stabilizes the temperature and reducesthe mechanical stresses of the flash lamp(s), but also serves to preheattarget tissue in a skin treatment region without causing any substantialdamage to non-target, surrounding tissue.

FIG. 10 provides a signal diagram of an illustrative light pulsesequence 1002 corresponding to the current waveform 902 of FIG. 9. Inthis embodiment, the intense light emissions that occur during the pulsestate of the flash lamps are substantially aligned with the pulsedurations of the electrical current waveform 902 and exhibitcorresponding oscillations in light output. In a temporary hair removaltreatment session, each of the four depicted light pulses (exhibitingwavelengths of interest) can emit about 3.75 joules of optical radiationfor an aggregate of 15 joules, which can be applied via a 2 squarecentimeter aperture to the skin resulting in a fluence of about 7.5joules per square centimeter. Of course, the number of pulses, energyper pulse, inter-pulse period, and other aspects of this illustrativewaveform 1002 and those of its related electrical waveforms 802, 902 canbe readily modified without materially departing from the teachings ofthe disclosed technology, so long as the intense light emissions duringthe lamps' pulse states and corresponding electric current and voltagepulses occur substantially within the time period in which the AC halfcycles are at or above the minimum operating voltage threshold 606.

FIG. 11 provides an illustrative thermal profile 1102 of target tissue(e.g., hair follicle, hair bulge, etc.) when subjected to the lightpulse sequence 1002 of FIG. 10 during a temporary hair removal treatmentsession. As shown, the temperature of the target tissue increasessubstantially during each light pulse and remains substantially at thesame temperature or slightly decreases during the inter-pulse periodbetween such light pulses. The aggregate effect of such light pulses isto increase the temperature of the target tissue to a level at whichtemporary hair removal will result.

Similarly, FIG. 12 provides an illustrative thermal profile 1202 ofnon-target tissue, such as the epidermis, when subjected to the lightpulse sequence 1002 of FIG. 10 during a temporary hair removal treatmentsession. As with the temperature profile 1102 of target tissue, thetemperature of the epidermis is increased during each light pulse, butdecreases more rapidly than the target tissue during the inter-pulseperiod. Accordingly, the temperature of the epidermis during thedermatologic treatment session can be maintained below any significantdamage threshold, while the desired thermal protocol is applied to thetarget tissue.

FIG. 13 depicts the circuit components and interconnections of anillustrative simmer power circuit 418 that can be made and operated inaccordance with the disclosed technology. As shown, and under thecontrol of the processor, simmer control circuit, and/or pulse durationprotection circuit of the control circuit 424, the simmer power circuit418 includes a transformer that increases the voltage level of directcurrent formed from the alternating current of the AC line source 426 toa desired level (750 volts for a dual flash lamp device). The simmerpower circuit 418 also includes a variety of capacitors that smooth outthe simmer power that is subsequently applied to the flash lamps 112before and during their simmer state.

FIG. 14 depicts the circuit components and interconnections of anillustrative trigger power circuit 420 that can be made and operated inaccordance with the disclosed technology. As shown, and under thecontrol of the processor and trigger control circuitry of the controlcircuit 424, the trigger power circuit 420 obtains some of the highervoltage energy from the transformer of the simmer power circuit 418 andfurther increases its voltage to about 10 kilovolts using its owntransformer. The resulting trigger pulse can then be used tocapacitively trigger the flash lamps 112 to instantiate their simmerstate as previously described.

FIG. 15 depicts the circuit components and interconnections of anillustrative pulse-drive circuit 422 that can be made and operated inaccordance with the disclosed technology. The pulse-drive circuit 422includes EMI filter circuitry 1502, rectifier circuitry 1504, and buckregulator circuitry 1506. The EMI filter circuit 1502 includes one ormore chokes and capacitive elements that effectively filter theelectrical energy to/from the AC line source 426 from electromagneticinterference. The filtered electrical energy can then be applied acrossa diode bridge of the rectifier circuit 1504 to full wave rectify thealternating current and then the rectified energy is applied tocapacitive elements within the circuit 1504 to smooth out the rectifiedAC into a high voltage direct current waveform. This high voltage directcurrent can then be applied to a field effect transistor or other powerswitching element 1508, which is selectively driven into conductive andnonconductive states under the control of the processor, currentregulation circuitry, and/or pulse duration protection circuitry of thecontrol circuit 424 as previously described. A snubber circuit 1510 canbe used across the power switching element 1508 to prevent ringing inthe switch during operation of the device 100. When the switch 1508 isin a conducting state, the electrical energy is passed through aninductor and diode circuit and applied to the electrodes of the flashlamps 112. The diode 1512 inhibits any substantial electrical energyfrom entering the pulse-drive circuit 422 from the simmer power circuit418 when the simmer circuit is engaged and thus prevents potentialdamage to circuit components of the pulse-drive circuit 422. A currentsensing resistor 1514 in the conducting path provides indicia to theprocessor and/or current regulator of the electrical current that isflowing through the flash lamps 112 at any given time and thus serves asa basis for the control circuit 424 to selectively enable/disable theswitch 1508, thereby controlling the electrical energy emissions to theflash lamps 112 that drive the light pulse sequence emissions.

FIG. 16 depicts the circuit components, interconnections, and interfacesof an illustrative control circuit 424 and AC line voltage detector 416that can be made and operated in accordance with the disclosedtechnology. The control circuit 424 includes a processor 1602, a simmercontrol circuit 1604, a trigger control circuit 1606, a currentregulator 1608, and a pulse duration protection circuit 1610, all ofwhich are designed and configured to operate the device 100 inaccordance with the disclosed embodiments.

While a number of embodiments and variations thereon have been describedabove, it is intended that these embodiments are for purposes ofillustration only and that numerous other variations are possible whilepracticing the teachings of the disclosed technology. For example, thedisclosed technology has been largely described in connection with hairgrowth management/removal applications, but can be applied to a widevariety of medical or cosmetic dermatologic treatments. The particularcircuit configurations and related functionality are also illustrativeand can be readily modified without materially departing from theteachings of this disclosure. Thus, while the invention has beenparticularly shown and described above with reference to preferredembodiments, the foregoing and other changes in form and detail may bemade therein by one skilled in the art without departing from the spiritand scope of the invention which is to be defined only by the appendedclaims.

1. A dermatologic treatment device, the device comprising: at least onepulse-able flash lamp capable of emitting sufficient light energy tofacilitate achievement of a desired cosmetic effect in a skin region;and a reflector optically coupled to the flash lamp and adapted toreflect at least some of the light energy emitted by the flash lamp; anoptical waveguide optically coupled to the reflector and adapted toconvey at least some of the reflected light energy therefrom; and anoptically transparent window optically coupled to the optical waveguideand adapted to receive at least some of the light energy conveyedthereby, wherein at least a portion of the optical waveguide is spacedapart from the window by a predetermined distance when the flash lamp isnot in its pulse state and wherein the distance is substantiallyeliminated when the flash lamp is in its pulse state.
 2. Thedermatologic treatment device of claim 1, wherein the flash lamp emitsat least one sequence of light pulses during its pulse state.
 3. Thedermatologic treatment device of claim 1, wherein the distance betweenthe optical waveguide and at the window facilitates cooling of thedevice, and wherein the substantially eliminated distance temporarilydecreases cooling of a least part of the device in favor of improvingoptical efficiency of the device.